1. Technical Field
The invention relates to an electronic circuit, and particularly relates to a reference voltage generating device and method thereof.
2. Related Art
Portable electronic products are all developed towards a design trend of low power consumption, fast booting speed, etc., so as to increase a usage and standby time of the electronic products under a same power capacity, and improve consumer's purchase willingness and user experience. Generally, an electronic circuit requires a reference voltage source non-related with an input power and an ambient temperature in internal thereof, such that a processing chip in the electronic circuit can determine accuracy of a signal according to a reference voltage. Namely, the reference voltage output by the reference voltage source is required to have characteristics of high power supply rejection ratio (PSRR), low noise, high accuracy, etc. Therefore, in order to make the reference voltage to satisfy the aforementioned requirements, the generated reference voltage is generally transmitted to a low-pass filter and/or a signal clipper (i.e. a damper) composed of resistors and capacitors for suitable adjustment.
Since the low-pass filter and/or signal clipper is added to an output terminal of the reference voltage source, a longer period of time such as a few hundred milliseconds after power on, and the reference voltage received by the processing chip can be accurate and stable. Namely, a stabilization time of the reference voltage after power on is probably too long, which delays a booting speed of the electronic product. A bandgap circuit with a smaller output current is generally used to serve as a generating device of the reference voltage, such that the capacitor at the output terminal has to take a longer time to stabilize the reference voltage. In component selection of the low-pass filter, if a resistor with a larger resistance is selected, the potential of the reference voltage is deviated and inaccurate, so that a larger capacitance and a smaller resistance are generally selected, though the stabilization time of the reference voltage is further prolonged.
Therefore, to design a reference voltage source occupying less circuit board area and capable of quickly providing the reference voltage to the processing chip is an urgently needed circuit design direction.